// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/base/dragdrop/drop_target_win.h"

#include <shlobj.h>

#include "base/logging.h"

namespace ui {

IDropTargetHelper* DropTargetWin::cached_drop_target_helper_ = NULL;

DropTargetWin::DropTargetWin(HWND hwnd)
    : hwnd_(hwnd)
    , ref_count_(0)
{
    DCHECK(hwnd);
    HRESULT result = RegisterDragDrop(hwnd, this);
    DCHECK(SUCCEEDED(result));
}

DropTargetWin::~DropTargetWin()
{
}

// static
IDropTargetHelper* DropTargetWin::DropHelper()
{
    if (!cached_drop_target_helper_) {
        CoCreateInstance(CLSID_DragDropHelper, 0, CLSCTX_INPROC_SERVER,
            IID_IDropTargetHelper,
            reinterpret_cast<void**>(&cached_drop_target_helper_));
    }
    return cached_drop_target_helper_;
}

///////////////////////////////////////////////////////////////////////////////
// DropTargetWin, IDropTarget implementation:

HRESULT DropTargetWin::DragEnter(IDataObject* data_object,
    DWORD key_state,
    POINTL cursor_position,
    DWORD* effect)
{
    // Tell the helper that we entered so it can update the drag image.
    IDropTargetHelper* drop_helper = DropHelper();
    if (drop_helper) {
        drop_helper->DragEnter(GetHWND(), data_object,
            reinterpret_cast<POINT*>(&cursor_position), *effect);
    }

    current_data_object_ = data_object;
    POINT screen_pt = { cursor_position.x, cursor_position.y };
    *effect = OnDragEnter(current_data_object_.get(), key_state, screen_pt, *effect);
    return S_OK;
}

HRESULT DropTargetWin::DragOver(DWORD key_state,
    POINTL cursor_position,
    DWORD* effect)
{
    // Tell the helper that we moved over it so it can update the drag image.
    IDropTargetHelper* drop_helper = DropHelper();
    if (drop_helper)
        drop_helper->DragOver(reinterpret_cast<POINT*>(&cursor_position), *effect);

    POINT screen_pt = { cursor_position.x, cursor_position.y };
    *effect = OnDragOver(current_data_object_.get(), key_state, screen_pt, *effect);
    return S_OK;
}

HRESULT DropTargetWin::DragLeave()
{
    // Tell the helper that we moved out of it so it can update the drag image.
    IDropTargetHelper* drop_helper = DropHelper();
    if (drop_helper)
        drop_helper->DragLeave();

    OnDragLeave(current_data_object_.get());

    current_data_object_ = NULL;
    return S_OK;
}

HRESULT DropTargetWin::Drop(IDataObject* data_object,
    DWORD key_state,
    POINTL cursor_position,
    DWORD* effect)
{
    // Tell the helper that we dropped onto it so it can update the drag image.
    IDropTargetHelper* drop_helper = DropHelper();
    if (drop_helper) {
        drop_helper->Drop(current_data_object_.get(),
            reinterpret_cast<POINT*>(&cursor_position), *effect);
    }

    POINT screen_pt = { cursor_position.x, cursor_position.y };
    *effect = OnDrop(current_data_object_.get(), key_state, screen_pt, *effect);
    return S_OK;
}

///////////////////////////////////////////////////////////////////////////////
// DropTargetWin, IUnknown implementation:

HRESULT DropTargetWin::QueryInterface(const IID& iid, void** object)
{
    *object = NULL;
    if (IsEqualIID(iid, IID_IUnknown) || IsEqualIID(iid, IID_IDropTarget)) {
        *object = this;
    } else {
        return E_NOINTERFACE;
    }
    AddRef();
    return S_OK;
}

ULONG DropTargetWin::AddRef()
{
    return ++ref_count_;
}

ULONG DropTargetWin::Release()
{
    if (--ref_count_ == 0) {
        delete this;
        return 0U;
    }
    return ref_count_;
}

DWORD DropTargetWin::OnDragEnter(IDataObject* data_object,
    DWORD key_state,
    POINT cursor_position,
    DWORD effect)
{
    return DROPEFFECT_NONE;
}

DWORD DropTargetWin::OnDragOver(IDataObject* data_object,
    DWORD key_state,
    POINT cursor_position,
    DWORD effect)
{
    return DROPEFFECT_NONE;
}

void DropTargetWin::OnDragLeave(IDataObject* data_object)
{
}

DWORD DropTargetWin::OnDrop(IDataObject* data_object,
    DWORD key_state,
    POINT cursor_position,
    DWORD effect)
{
    return DROPEFFECT_NONE;
}

} // namespace ui
